Sulphate–light scattering ratio as an index of the role of sulphur in tropospheric optics

Abstract

THE optical properties of the non-cloudy atmosphere are determined by a fixed component, the molecular gases, and a variable component, the aerosol particles. The optical effects of these two components have been subject to speculation and scientific investigation for many years. The major features of molecular and particle optics are reasonably well understood^1–3 and instrumental techniques have been developed to measure extinction of light⁴, scattering phase function^5,6 and the scattering component of extinction⁷. Few data or analyses have, however, been presented which consider the chemical nature of the aerosol in terms of its effects on radiative properties, although a few exceptions can be cited^8–12. Experimental evidence quantitatively linking the chemical composition of aerosol particles with the macroscopic optical consequences is sparse, but here we mention one approach relating chemical and optical measurements on regional scale air masses and present preliminary data.